Cooling of a semiconductor by luminescence up-conversion

We report the observation of phonon-mediated up-conversion of luminescence in a GaAs quantum well. This opens the possibility of light-induced lattice cooling in a semiconductor. Under appropriate conditions, pumping the samp le with light at the energy of the heavy-hole exciton, we observe light-hol e exciton emission, which lies similar to 10 meV above the excitation energ y. The use of an external magnetic field together with the resolution of ex cited excitonic states provides an internal thermometer to monitor the samp le temperature. Temperature drops as large as 10% of the initial temperatur e are observed for pump densities of 4 W cm(-2). (C) 1999 American Institut e of Physics. [S0003-6951(99)00435-0].